提取两个时间点的天数差

作者：郝春利
转贴请注明出处： http://blog.youkuaiyun.com/froole

提取两个时间点的天数差——看上去一个及其单纯的问题，但是，考虑到不同年份、闰年等因素，想要写一个可以广泛使用的却非常麻烦。
以下是loveapple工程中我写的一个提取不同时间点的天数的代码，如有不足，希望各路大虾指正。

1. /*
2.  * $Header$
3.  * $Author$
4.  * $Revision$
5.  * $Date$
6.  *
7.  * ====================================================================
8.  *
9.  * Copyright (C) 2008 by www.loveapple.cn
10.  *
11.  * All copyright notices regarding loveapple and loveapple CoreLib
12.  * MUST remain intact in the scripts, documents and source code.
13.  *
14.  * This library is free software; you can redistribute it and/or
15.  * modify it under the terms of the GNU Lesser General Public
16.  * License as published by the Free Software Foundation; either
17.  * version 3 of the License, or (at your option) any later version.
18.  *
19.  * This library is distributed in the hope that it will be useful,
20.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
21.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
22.  * Lesser General Public License for more details.
23.  *
24.  * You should have received a copy of the GNU Lesser General Public
25.  * License along with this library; if not, write to the Free Software
26.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
27.  *
28.  * Correspondence and Marketing Questions can be sent to:
29.  * info at loveapple
30.  *
31.  * @author: loveapple
32.  */
33. package cn.loveapple.common.util;
35. import java.util.Calendar;
38. /**
39.  * @author loveapple
40.  * @since 2008/09/16
41.  * @version $Revision:$
42.  */
43. public final class DateUtils {
44.     /**
45.      * Get from start to end days.
46.      * @param start
47.      * @param end
48.      * @return start-end days
49.      */
50.     public final static int diffDayCount(Calendar start, Calendar end){
51.         int result = 0;
52.         DayDate startDay = new DayDate(start);
53.         DayDate endDay = new DayDate(end);
54.         if(startDay.equals(endDay) || startDay.equals(startDay.getLastDay(endDay))){
55.             return result;
56.         }
57.         
58.         if(startDay.year == endDay.year){
59.             return endDay.dayOfY - startDay.dayOfY;
60.         }else{
61.             Calendar tmp = Calendar.getInstance();
62.             result = startDay.calendar.getActualMaximum(Calendar.DAY_OF_YEAR) - startDay.dayOfY;
63.             for(int i = startDay.year+1; i < endDay.year; i++){
64.                 tmp.set(i, tmp.get(Calendar.MONTH), tmp.get(Calendar.DAY_OF_MONTH));
65.                 result += tmp.getActualMaximum(Calendar.DAY_OF_YEAR);
66.             }
67.             result += endDay.dayOfY;
68.         }
69.         
70.         return result;
71.     }
72.     
73.     /**
74.      * Express a data of day.
75.      * 
76.      * @author loveapple
77.      * @since 2008/09/16
78.      * @version $Revision:$
79.      */
80.     private static class DayDate{
81.         int year;
82.         int month;
83.         int dayOfM;
84.         int dayOfY;
85.         Calendar calendar;
86.         public DayDate(Calendar calendar) {
87.             year = calendar.get(Calendar.YEAR);
88.             month = calendar.get(Calendar.MONTH);
89.             dayOfM = calendar.get(Calendar.DAY_OF_MONTH);
90.             dayOfY = calendar.get(Calendar.DAY_OF_YEAR);
91.             this.calendar = calendar;
92.         }
93.         
94.         /**
95.          * 
96.          * {@inheritDoc}
97.          */
98.         @Override
99.         public boolean equals(Object obj){
100.             if(obj instanceof DayDate){
101.                 DayDate day = (DayDate)obj;
102.                 if(day.year == year && day.dayOfY == dayOfY){
103.                     return true;
104.                 }
105.                 return false;
106.             }
107.             return false;
108.         }
109.         
110.         /**
111.          * 
112.          * @param day
113.          * @return
114.          */
115.         public DayDate getLastDay(DayDate day){
116.             if(day.year == year){
117.                 if(day.dayOfY < dayOfY){
118.                     return this;
119.                 }
120.                 return day;
121.             }else if(day.year < year){
122.                 return this;
123.             }
124.             return day;
125.         }
126.     }
127. }

测试代码

1. public static void main(String[] args) {
2.         Calendar today = Calendar.getInstance();
3.         Calendar startDay1 = Calendar.getInstance();
4.         startDay1.set(2000, 1, 2);
5.         Calendar startDay2 = Calendar.getInstance();
6.         startDay2.set(today.get(Calendar.YEAR), today.get(Calendar.MONTH), 1);
7.         Calendar startDay3 = Calendar.getInstance();
8.         startDay3.set(today.get(Calendar.YEAR), 1, 1);
9.         
10.         SimpleDateFormat format = new SimpleDateFormat("yyyy/MM/dd");
11.         
12.         System.out.println(format.format(startDay1.getTime()) + " - " + format.format(today.getTime()) + " [" + DateUtils.diffDayCount(startDay1, today) + "]");
13.         System.out.println(format.format(startDay2.getTime()) + " - " + format.format(today.getTime()) + " [" + DateUtils.diffDayCount(startDay2, today) + "]");
14.         System.out.println(format.format(startDay3.getTime()) + " - " + format.format(today.getTime()) + " [" + DateUtils.diffDayCount(startDay3, today) + "]");
15.     }